Reactive dyes are widely used in the treatment of cotton, wool and regenerated cellulose because good fastness is achieved with a wide range of shades. After the dyeing stage it is necessary to remove the unreacted dye from the textile to ensure all the dye remaining on the textile surface is fast.
This washing stage is a lengthy process because a number of separate washing baths have to be used in sequence to ensure the final stage removes the remnants of dye only loosely bound to the surface. Thus the washing procedure uses a considerable amount of water and chemicals added to the washing baths to assist dye removal. The baths are usually operated at a temperature in the range 60.degree. C. to 100.degree. C. and therefore considerable heat energy is required. An additional consideration is the large quantity of water which contains washed off dye and which has to be disposed of via an effluent system. Environmental requirements are becoming more restrictive on the discharge of water containing coloured material and there is, in any case, a poor visual impact on water courses by such discharge. The process of reactive dyeing and washing is described in "The Dyeing of Cellulosic Fibres" published Dyers Company Trust 1986.